1. Field of the Invention
The invention relates to an image reading device in which a cold-cathode lamp is used as a light source for an image reading, and to a storage medium that stores programs for controlling the image reading device.
2. Description of the Related Art
In general, in a digital image reading device, light emitted from a light source for an image reading irradiates a read medium, such as an original document. The light reflected from the read medium is received by an image sensor, so that digital image signals, corresponding to images on the read medium, are obtained. In an analog image reading device, the light reflected from the read medium is guided onto a surface, such as that of a photo-conductive drum. Electrostatic latent images corresponding to images on the read medium are formed on the surface of the photo-conductive drum.
In the image reading devices, various light-emitting devices are used as a light source for the image reading. Among the light-emitting devices, a cold-cathode lamp has the advantages of a relatively low cost and a great amount of light emitted, so that images on the read medium can be read at a higher speed.
However, the cold-cathode lamp has a disadvantage of a certain length of time required, after a voltage is applied, to emit light at a brightness sufficient for the image reading. Therefore, when a user performs an image reading operation, a certain length of time is required to start the image reading after the voltage is applied to the cold-cathode lamp. Accordingly, the user cannot start the image reading operation immediately.
To reduce the time wasted before the image reading is started as much as possible, one possible solution is to continuously light the cold-cathode lamp. In a conventional image reading device, the cold-cathode lamp is continuously lit, until the power of the image reading device is turned off, after the power is turned on. If the cold-cathode lamp is continuously lit, as in the conventional image reading device, the brightness of the cold-cathode lamp will be sufficient when the image reading is designated by the user. Consequently, the user can start the image reading operation immediately, without wasting the time before the image reading is started.
However, the operating life of the cold-cathode lamp gradually decreases as the cumulative lighting hours increases. Accordingly, the brightness of the cold-cathode lamp is reduced, resulting in the insufficient brightness for the image reading. It is known that the operating life of the cold-cathode lamp is greatly affected by a lamp wall temperature. Specially, when the cold-cathode lamp is lit, if its wall temperature is low (at a low ambient temperature), the operating life of the lamp becomes extremely shortened. As the cold-cathode lamp is continuously lit, the life of the cold-cathode lamp expires within a short time, according to the ambient temperatures. Specially, when the cold-cathode lamp is employed, as a light source for the image reading in an apparatus, for example, a multi-function device, having various functions, such as facsimile functions, copying functions, printer functions, and image scanner functions, the power of the apparatus normally stays on, so that the cold-cathode lamp is continuously lit, day and night in all seasons. Consequently, the operating life of the lamp becomes shortened, especially when the cold-cathode lamp is continuously lit at a low ambient temperature, as described above. This leads to the frequent replacement of the lamp, and the costs, labor, and time for its replacement become significant.
One aspect of the invention is to provide an image reading device that includes a cold-cathode lamp, as a light source for image reading, and that immediately starts an image reading operation under normal room conditions, after a user""s designation, and prolongs the operating life of the cold-cathode lamp as much as possible. Another aspect of the invention is to provide a method for controlling the image reading device and a storage medium that stores a program for controlling the image reading device.
According to one aspect of the invention, there is provided an image reading device including a cold-cathode lamp as a light source for image reading. The cold-cathode lamp is lit even when image reading is not performed. The image reading device may include a temperature detecting device that detects a wall temperature of the cold-cathode lamp or a temperature that has a correlation to the lamp wall temperature, and a lighting-out control device that lights out the cold-cathode lamp when the image reading is not performed and when a temperature detected by the temperature detecting device is equal to or below a first predetermined temperature.
In this image reading device, the lighting-out control device turns off the cold-cathode lamp when the image reading is not performed and when a temperature detected by the temperature detecting device is equal to or below the first predetermined temperature. Accordingly, an image reading operation can be immediately started, under normal room conditions, after a user""s designation. In addition, the operating life of the cold-cathode lamp can be prolonged as much as possible. Included in the image reading device are such types that light reflected from read medium, such as an original document, is received by an image sensor, and that the light reflected from the read medium, is guided onto a surface of a photo-conductive member.
During the time when a multi-function device (MFD) including the image reading device of the invention is usually used, for example, from 8 a.m. to 8 p.m., the room temperature of, for example, an office will not so decrease, except for winter. In such seasons when a user feels cool, the office is generally heated during the above-described time, so that the room temperature does not decrease very much. Therefore, the cold-cathode lamp is lit during such time, and the image reading operation may be started immediately after the user presses, for example, a copy key of the MFD, so as to make a copy of the read medium. As the above-described time goes by and the heat in the office is turned off, the room temperature gradually decreases. Accordingly, the lighting-out control device may turn off the cold-cathode lamp.
Because the cold-cathode lamp is lit during the time when the user frequently uses the MFD, the copying operation can be started immediately. In addition, during the time when the user does not usually use the MFD, the cold-cathode lamp is not lit. Accordingly, the cumulative hours of lightning at lower temperatures will not be increased, so that the operating life of the cold-cathode lamp is prolonged as much as possible.
The cold-cathode lamp may be lit up at the time when the user presses the copy key first on the day, or when the room temperature exceeds the setting temperature.
The temperature detecting device is preferably disposed adjacent to the cold-cathode lamp. However, the temperature detecting device may be disposed on a surface of a case of the MFD, as a temperature that has a correlation to the lamp wall temperature can be detected thereon.
The first predetermined temperature may be set slightly lower than the ambient temperature during the time when the user frequently uses the MFD. The first predetermined temperature may be set prior to shipment, or the user can change the first predetermined temperature setting, according to geographic areas or seasons.
As the cold-cathode lamp lights for a first predetermined time or more, the lighting-out control device may turn off the cold-cathode lamp, even when the temperature detected by the temperature detecting device is not equal to or below the first predetermined temperature, if image reading is not performed. Accordingly, the operating life of the cold-cathode lamp may be prolonged as much as possible.
When the temperature at night is high, the cold-cathode lamp may not be controlled by the temperature, so as to be turned off. However, the cold-cathode lamp may be turned off, by limiting the continuous lighting hours thereof.
Further, the lighting-out control device may vary the first predetermined time, based on the temperature detected by the temperature detecting device. Accordingly, the operating life of the cold-cathode lamp may be prolonged as much as possible.
For example, when the detected temperature is equal to or below the setting temperature, the first predetermined time may be set to 1 hour. When the detected temperature exceeds the setting temperature, the first predetermined time may be set to 14 hours. Such settings reduce the lighting hours of the cold-cathode lamp at temperatures equal to or below the setting temperature. Accordingly, the operating life of the cold-cathode lamp can be sufficiently extended. As the cold-cathode lamp is lit during the time when the MFD is frequently used and when the room temperature of the office is low, the operating of the cold-cathode lamp is remarkably shortened. If the first predetermined temperature is set high, to prevent the above-described situation, the cold-cathode lamp will often not be lit when image reading is not performed. This causes an inconvenience to the user. Therefore, by setting the first predetermined time to, for example, 1 hour when the detected temperature is equal to or below the setting temperature, the cold-cathode lamp may be turned off, such as when the user does not use the MFD, to make a copy of the read medium for an hour or more, after the cold-cathode lamp is lit.
For the first predetermined time, three or more settings, rather than two settings, may be made.
The first predetermined time may be determined based on the temperature detected at the time when the cold-cathode lamp starts to light up, or the latest temperature among temperatures detected at a certain cycle while the cold-cathode lamp is lighting.
The image reading device of the invention may include a lighting-up control device that turns on the cold-cathode lamp when the cold-cathode lamp is not lit and when the temperature detected by the temperature detecting device is equal to or above a second predetermined temperature which is higher than the first predetermined temperature.
In the image reading device, the cold-cathode lamp may be turned on automatically. More specifically, the cold-cathode lamp is turned off as the room temperature decreases and the detected temperature is equal to or below the first predetermined temperature. However, the cold-cathode lamp, which is not lit, is automatically turned on, as the room temperature goes up when the morning comes or when the heater is turned on, and the detected temperature is equal to or above a second predetermined temperature. Accordingly, the user who makes a copy of the read medium first in the day, does not have to wait until the cold-cathode lamp reaches a brightness required for the image reading.
The second predetermined temperature may be determined based on the first predetermined temperature. The second predetermined temperature may be set prior to shipment, or set by the user, according to geographic areas or seasons. Further, a structure such that a certain range given to the first predetermined temperature is automatically set as the second predetermined temperature, may be employed.
Further, the image reading device of the invention may include an image reading prohibiting device that prohibits the image reading from being started, until a second predetermined time elapses after the cold-cathode lamp starts to light, and an image reading prohibiting time varying device that varies the second predetermined time, based on the temperature detected by the temperature detecting device.
In the image reading device, the time until the image reading is started after the cold-cathode lamp starts to light can be reduced to a minimum, according to the lamp wall temperatures, so that the time that the user has to wait can be greatly reduced.
The time required for the cold-cathode lamp to reach the proper brightness for the image reading, after the lamp is started to be lit up varies according to the lamp wall temperatures. Therefore, by varying the time until the image reading is started, after the cold-cathode lamp starts to light, according to the detected lamp wall temperature, the image reading can be started at the time when the cold-cathode lamp reaches the proper brightness for image reading. Consequently, when the user presses, for example, a copy key, with the cold-cathode lamp being turned off, the copying operation may be started with the minimum waiting time.
According to another aspect of the invention, there is provided a storage medium storing a program for controlling an image reading device including a cold-cathode lamp as a light source for image reading. The cold-cathode lamp is lit even when the image reading is not performed. The storage medium may store a lighting-out control program for turning off the cold-cathode lamp when the image reading is not performed and when a temperature detected by a temperature detecting device that detects a wall temperature of the cold-cathode lamp or a temperature that has correlation to the lamp wall temperature, is equal to or below a first predetermined temperature.
By activating a central processing unit (CPU) based on the program stored in the storage medium, the above-described operations of the image reading device can be achieved.
The storage medium may be a non-volatile semiconducting memory. Other than the non-volatile semiconducting memory, the storage medium may be a volatile semiconducting memory backed up by, for example, a battery, a compact disk read only memory (CD-ROM), a flexible disk, or a hard disk.